Heat exchange apparatus

ABSTRACT

A heat exchange apparatus that performs heat exchange between a refrigerant and a temperature-adjusted unit includes: a compressor that circulates the refrigerant; a heat exchanger that performs heat exchange between the refrigerant and outside air; an expansion valve that reduces a pressure of the refrigerant; a heat exchanger that performs heat exchange between the refrigerant and air-conditioning air; a cooling passage that forms a path for the refrigerant to flow between the heat exchanger and the expansion valve; and a heating passage that forms a path for the refrigerant to flow between the expansion valve and the heat exchanger. The temperature-adjusted unit is disposed to be capable of exchanging heat with the refrigerant flowing through the cooling passage and to be capable of exchanging heat with the refrigerant flowing through the heating passage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a heat exchange apparatus, and moreparticularly to a heat exchange apparatus that performs heat exchangebetween a refrigerant flowing through a vapor compression refrigerationcycle and a temperature-adjusted unit subjected to temperatureadjustment.

2. Description of Related Art

In the related art pertaining to a motor cooling apparatus for cooling adrive motor, for example, Japanese Patent Application Publication No.2005-218271 (JP 2005-218271 A) proposes a technique in which, when atemperature difference between a temperature of a drive motor and an oiltemperature increases beyond a predetermined value, oil cooled by an oilcooler is supplied to the drive motor, and when the temperaturedifference between the temperature of the drive motor and the oiltemperature falls to or below the predetermined value, oil cooling bythe oil cooler is stopped.

In another proposed technique, a heat generating body is cooled using avapor compression refrigeration cycle employed as a vehicleair-conditioning apparatus. For example, Japanese Patent ApplicationPublication No. 2007-69733 (JP 2007-69733 A) discloses a system in whicha heat exchanger that exchanges heat with air-conditioning air and aheat exchanger that exchanges heat with a heat generating body aredisposed in parallel in a refrigerant passage extending from anexpansion valve to a compressor, and the heat generating body is cooledby a refrigerant used in an air-conditioning apparatus. Japanese PatentApplication Publication No. 2005-90862 (JP 2005-90862 A) discloses acooling system in which heat generating body cooling means for cooling aheat generating body is provided in a bypass passage that bypasses apressure reducer, an evaporator, and a compressor of an air-conditioningrefrigeration cycle.

Japanese Patent Application Publication No. 11-223406 (JP 11-223406 A)discloses a configuration for causing a refrigerant of a heat pump cycleto absorb waste heat from a heat generating body such as a powertransistor. Japanese Patent Application Publication No. 9-290622 (JP9-290622 A) discloses a technique in which waste heat from a heatgenerating part installed in a vehicle is collected and absorbed into arefrigerant used for gas injection, thereby effectively improving aheating ability when an outside air temperature is low while suppressingan increase in power consumption.

As a method of cooling a transaxle installed in a vehicle, heatgenerated by a heat generating member such as a motor/generator or agear constituting the transaxle may be collected in an AutomaticTransmission Fluid (ATF). The ATF may then be pumped to a heat exchangeron the exterior of the transaxle in order to exchange heat with coolingwater or a refrigerant used for air-conditioning. The ATF must be cooledin order to protect components such as a coil and a magnet of themotor/generator, suppress deterioration of the ATF, and so on. However,the ATF does not always need to be cooled. When the ATF is overcooled, aviscosity of the ATF increases, and as a result, the gear may belubricated insufficiently and an increase in friction loss may occur.The ATF is therefore preferably warmed to an appropriate temperature.

SUMMARY OF THE INVENTION

The invention has been designed in consideration of the problemdescribed above, and provides a heat exchange apparatus with which atemperature of a temperature-adjusted unit can be adjusted appropriatelythrough heat exchange with a refrigerant.

According to an aspect of the invention, a heat exchange apparatus thatperforms heat exchange between a refrigerant and a temperature-adjustedunit includes: a compressor that compresses the refrigerant in order tocirculate the refrigerant through the heat exchange apparatus; a firstheat exchanger that performs heat exchange between the refrigerant andoutside air; a first pressure reducer that reduces a pressure of therefrigerant; a second heat exchanger that performs heat exchange betweenthe refrigerant and air-conditioning air; a first passage that forms apath for the refrigerant to flow between the first heat exchanger andthe first pressure reducer; and a second passage that forms a path forthe refrigerant to flow between the first pressure reducer and thesecond heat exchanger. The temperature-adjusted unit is disposed to becapable of exchanging heat with the refrigerant flowing through thefirst passage and to be capable of exchanging heat with the refrigerantflowing through the second passage.

The heat exchange apparatus described above may further include afour-way valve that switches between a refrigerant flow from thecompressor to the first heat exchanger and a refrigerant flow from thecompressor to the second heat exchanger.

The heat exchange apparatus described above may further include: a thirdpassage connected in parallel with the first passage on the refrigerantpath between the first heat exchanger and the first pressure reducer;and a first flow control valve that adjusts a flow rate of therefrigerant flowing through the first passage and a flow rate of therefrigerant flowing through the third passage.

The heat exchange apparatus described above may further include: afourth passage connected in parallel with the second passage on therefrigerant path between the first pressure reducer and the second heatexchanger; and a second flow control valve that adjusts a flow rate ofthe refrigerant flowing through the second passage and a flow rate ofthe refrigerant flowing through the fourth passage.

The heat exchange apparatus described above may further include a firstopen/close valve that opens and closes the first passage, and a secondopen/close valve that opens and closes the second passage. The secondopen/close valve may be closed when the first open/close valve is open,and the second open/close valve may be open when the first open/closevalve is closed.

The heat exchange apparatus described above may further include a secondpressure reducer that is provided in the first passage between the firstheat exchanger and the temperature-adjusted unit in order to reduce thepressure of the refrigerant.

The heat exchange apparatus described above may further include: a fifthpassage that is connected in parallel with a path passing through thesecond pressure reducer on a path that forms a part of the first passageand passes through the temperature-adjusted unit and the first heatexchanger; and a third open/close valve that is provided in the fifthpassage in order to open and close the fifth passage.

With the heat exchange apparatus according to the invention, thetemperature of the temperature-adjusted unit can be adjustedappropriately by performing heat exchange between the refrigerant andthe temperature-adjusted unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages, and technical and industrial significance ofthis invention will be described in the following detailed descriptionof example embodiments of the invention with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a schematic view showing a configuration of a heat exchangeapparatus according to a first embodiment of the invention;

FIG. 2 is a Mollier chart showing states of a refrigerant during acooling operation of a vapor compression refrigeration cycle accordingto the first embodiment;

FIGS. 3A, 3B, 3C and 3D are schematic views showing opening control of aflow control valve shown in FIG. 1;

FIG. 4 is a schematic view showing the heat exchange apparatus in acondition where a four-way valve shown in FIG. 1 has been switched;

FIG. 5 is a Mollier chart showing states of the refrigerant during aheating operation of the vapor compression refrigeration cycle accordingto the first embodiment;

FIG. 6 is a schematic view showing the heat exchange apparatus when atemperature-adjusted unit according to the first embodiment, shown inFIG. 4, is heated;

FIG. 7 is a Mollier chart showing states of the refrigerant used in thevapor compression refrigeration cycle according to the first embodimentwhen the temperature-adjusted unit is heated;

FIG. 8 is a schematic view showing a configuration of a heat exchangeapparatus according to a second embodiment;

FIG. 9 is a Mollier chart showing states of a refrigerant during acooling operation of a vapor compression refrigeration cycle accordingto the second embodiment;

FIG. 10 is a schematic view showing the heat exchange apparatusaccording to the second embodiment in a condition where a four-way valveshown in FIG. 9 has been switched;

FIG. 11 is a Mollier chart showing states of the refrigerant during aheating operation of the vapor compression refrigeration cycle accordingto the second embodiment;

FIG. 12 is a schematic view showing the heat exchange apparatus when atemperature-adjusted unit according to the second embodiment, shown inFIG. 10, is heated;

FIG. 13 is a Mollier chart showing states of the refrigerant used in thevapor compression refrigeration cycle according to the second embodimentwhen the temperature-adjusted unit is heated;

FIG. 14 is a schematic view showing a configuration of a heat exchangeapparatus according to a third embodiment;

FIG. 15 is a Mollier chart showing states of a refrigerant during acooling operation of a vapor compression refrigeration cycle accordingto the third embodiment;

FIG. 16 is a schematic view showing the heat exchange apparatusaccording to the third embodiment in a condition where a four-way valveshown in FIG. 14 has been switched; and

FIG. 17 is a schematic view showing the heat exchange apparatus when atemperature-adjusted unit according to the third embodiment, shown inFIG. 16, is heated.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described below on the basis of thedrawings. Note that in the following drawings, identical orcorresponding parts have been allocated identical reference numerals,and description thereof has not been repeated.

FIG. 1 is a schematic view showing a configuration of a heat exchangeapparatus according to a first embodiment. As shown in FIG. 1, a heatexchange apparatus 1 includes a vapor compression refrigeration cycle10. The vapor compression refrigeration cycle 10 is installed in avehicle in order to cool and heat a vehicle interior of the vehicle, forexample. Cooling is performed using the vapor compression refrigerationcycle 10 when, for example, a switch for performing cooling is switchedON or an automatic control mode for adjusting a temperature in apassenger compartment of the vehicle to a set temperature automaticallyhas been selected and the temperature in the passenger compartment ishigher than the set temperature. Heating is performed using the vaporcompression refrigeration cycle 10 when, for example, a switch forperforming heating is switched ON or the automatic control mode has beenselected and the temperature in the passenger compartment is lower thanthe set temperature.

The vapor compression refrigeration cycle 10 includes a compressor 12, aheat exchanger 14 serving as a first heat exchanger, an expansion valve16 serving as an example of a pressure reducer, and a heat exchanger 18serving as a second heat exchanger. The vapor compression refrigerationcycle 10 also includes a four-way valve 13. The four-way valve 13 isdisposed to be capable of switching between a refrigerant flow travelingfrom the compressor 12 toward the heat exchanger 14 and a refrigerantflow traveling from the compressor 12 toward the heat exchanger 18.

The compressor 12 is operated using a motor or an engine installed inthe vehicle as a power source to compress refrigerant gas adiabaticallyinto superheated refrigerant gas. The compressor 12 aspirates andcompresses a gas phase refrigerant that flows when the vapor compressionrefrigeration cycle 10 is operative, and discharges a high-temperature,high-pressure gas phase refrigerant. By discharging the refrigerant, thecompressor 12 circulates the refrigerant through the vapor compressionrefrigeration cycle 10.

The heat exchangers 14, 18 respectively include a tube through which therefrigerant flows and a fin that performs heat exchange between therefrigerant flowing through the tube and air on the periphery of theheat exchangers 14, 18. The heat exchangers 14, 18 perform heat exchangebetween the refrigerant and either an air flow supplied by a naturalbreeze generated as the vehicle travels or an air flow supplied by afan.

The expansion valve 16 expands a high-pressure liquid phase refrigerantby ejecting the liquid phase refrigerant through a small hole. As aresult, the high-pressure liquid phase refrigerant is changed into alow-temperature, low-pressure mist-form refrigerant. The expansion valve16 reduces a pressure of a condensed refrigerant liquid to generate wetvapor in a gas-liquid mixed state. Note that the pressure reducer forreducing the pressure of the refrigerant liquid is not limited to theexpansion valve 16 that performs throttle expansion, and may also be acapillary tube.

The vapor compression refrigeration cycle 10 further includesrefrigerant passages 21 to 26. The refrigerant passage 21 connects thecompressor 12 to the four-way valve 13. The refrigerant flows from thecompressor 12 to the four-way valve 13 through the refrigerant passage21. The refrigerant passage 22 connects the four-way valve 13 to theheat exchanger 14. The refrigerant flows from one of the four-way valve13 and the heat exchanger 14 to the other through the refrigerantpassage 22. The refrigerant passage 23 connects the heat exchanger 14 tothe expansion valve 16. The refrigerant flows from one of the heatexchanger 14 and the expansion valve 16 to the other through therefrigerant passage 23.

The refrigerant passage 24 connects the expansion valve 16 to the heatexchanger 18. The refrigerant flows from one of the expansion valve 16and the heat exchanger 18 to the other through the refrigerant passage24. The refrigerant passage 25 connects the heat exchanger 18 to thefour-way valve 13. The refrigerant flows from one of the heat exchanger18 and the four-way valve 13 to the other through the refrigerantpassage 25. The refrigerant passage 26 connects the four-way valve 13 tothe compressor 12. The refrigerant flows from the four-way valve 13 tothe compressor 12 through the refrigerant passage 26.

The vapor compression refrigeration cycle 10 is formed by connecting thecompressor 12, the heat exchanger 14, the expansion valve 16, and theheat exchanger 18 to each other using the refrigerant passages 21 to 26.Note that carbon dioxide, a hydrocarbon such as propane or isobutane,ammonia, water, or the like, for example, may be used as the refrigerantof the vapor compression refrigeration cycle 10.

A first passage and a refrigerant passage 23 a serving as a thirdpassage are connected in parallel and provided on a path along which therefrigerant flows between the heat exchanger 14 and the expansion valve16. The refrigerant passage 23 a forms a part of the refrigerant passage23 serving as the refrigerant path between the heat exchanger 14 and theexpansion valve 16. A heat exchange unit 30 is provided on the firstpassage. The heat exchange unit 30 is provided on the refrigerant pathbetween the heat exchanger 14 and the expansion valve 16. The heatexchange unit 30 includes a temperature-adjusted unit 31 that issubjected to temperature adjustment, and a cooling passage 32constituted by a pipe through which the refrigerant flows. The heatexchange apparatus 1 includes the refrigerant passage 23 a as a paththat does not pass through the heat exchange unit 30, and includesrefrigerant passages 52, 54, 55 and the cooling passage 32 as a paththat passes through the heat exchange unit 30. The refrigerant pathbetween the heat exchanger 14 and the expansion valve 16 bifurcates suchthat a part of the refrigerant flows to the heat exchange unit 30.

The refrigerant passages 52, 54, 55 are provided as a path along whichthe refrigerant flows to the cooling passage 32. One end portion of thecooling passage 32 is connected to the refrigerant passage 54, andanother end portion of the cooling passage 32 is connected to therefrigerant passage 55. The refrigerant passage 52 and the refrigerantpassage 54 communicate via an open/close valve 53. The refrigerant flowsfrom the refrigerant passage 23 into the cooling passage 32 througheither the refrigerant passages 52, 54 or the refrigerant passage 55.The refrigerant that flows through the cooling passage 32 exchanges heatwith the temperature-adjusted unit 31, and then returns to therefrigerant passage 23 through the other of the refrigerant passages 52,54 and the refrigerant passage 55. The first passage connected to therefrigerant passage 23 a in parallel therewith includes the refrigerantpassages 52, 54 on the heat exchanger 14 side of the heat exchange unit30, the cooling passage 32 provided in the heat exchange unit 30, andthe refrigerant passage 55 on the expansion valve 16 side of the heatexchange unit 30. The open/close valve 53 opens and closes the firstpassage.

The refrigerant flowing between the heat exchanger 14 and the expansionvalve 16 flows through the cooling passage 32. While flowing through thecooling passage 32, the refrigerant cools the temperature-adjusted unit31 by drawing heat from the temperature-adjusted unit 31. The heatexchange unit 30 is structured such that heat exchange can be performedbetween the temperature-adjusted unit 31 and the refrigerant in thecooling passage 32. In this embodiment, the heat exchange unit 30includes the cooling passage 32, which is formed such that an outerperipheral surface thereof directly contacts a casing of thetemperature-adjusted unit 31, for example. The cooling passage 32includes a part that is adjacent to the casing of thetemperature-adjusted unit 31. In this part, heat exchange can beperformed between the refrigerant flowing through the cooling passage 32and the temperature-adjusted unit 31.

The temperature-adjusted unit 31 is cooled by being directly connectedto the outer peripheral surface of the cooling passage 32 that forms apart of the refrigerant path extending from the heat exchanger 14 to theexpansion valve 16 of the vapor compression refrigeration cycle 10.Since the temperature-adjusted unit 31 is disposed on an exterior of thecooling passage 32, the temperature-adjusted unit 31 does not interferewith the refrigerant flow flowing through the interior of the coolingpassage 32. Accordingly, pressure loss in the vapor compressionrefrigeration cycle 10 does not increase, and therefore thetemperature-adjusted unit 31 can be cooled without increasing a power ofthe compressor 12.

Alternatively, the heat exchange unit 30 may include an arbitraryconventional heat pipe that is interposed between thetemperature-adjusted unit 31 and the cooling passage 32. In this case,the temperature-adjusted unit 31 is connected to the outer peripheralsurface of the cooling passage 32 via the heat pipe and cooled by heattransferred from the temperature-adjusted unit 31 to the cooling passage32 via the heat pipe. By setting the temperature-adjusted unit 31 as aheat pipe heating portion and setting the cooling passage 32 as a heatpipe cooling portion, a heat transfer efficiency between the coolingpassage 32 and the temperature-adjusted unit 31 can be improved, leadingto an improvement in an efficiency with which the temperature-adjustedunit 31 is cooled. A Wick Heating Pipe, for example, may be used.

Heat can be transferred reliably from the temperature-adjusted unit 31to the cooling passage 32 using the heat pipe, and therefore thetemperature-adjusted unit 31 and the cooling passage 32 may be distancedfrom each other, thereby eliminating the need to provide the coolingpassage 32 in a complicated arrangement to ensure that the coolingpassage 32 contacts the temperature-adjusted unit 31. As a result, adisposal freedom of the temperature-adjusted unit 31 can be improved.

The refrigerant passages 52, 54, 55 and the cooling passage 32 servingas the path that passes through the heat exchange unit 30 are providedin parallel with the refrigerant passage 23 a serving as the path thatdoes not pass through the heat exchange unit 30 as the path along whichthe refrigerant flows between the heat exchanger 14 and the expansionvalve 16. A cooling system for the temperature-adjusted unit 31,including the refrigerant passages 52, 54, 55, is connected in parallelwith the refrigerant passage 23 a. By providing the path of therefrigerant that flows between the heat exchanger 14 and the expansionvalve 16 without passing through the heat exchange unit 30 in parallelwith the path of the refrigerant that passes through the heat exchangeunit 30 and causing only a part of the refrigerant to flow to therefrigerant passages 52, 54, 55, only a part of the refrigerant flowingbetween the heat exchanger 14 and the expansion valve 16 is caused toflow to the heat exchange unit 30.

A situation in which an amount of refrigerant required to cool thetemperature-adjusted unit 31 is caused to flow to the refrigerantpassages 52, 54, 55 such that all of the refrigerant flows to the heatexchange unit 30 does not occur in the heat exchange unit 30. Hence, thetemperature-adjusted unit 31 can be cooled appropriately, andovercooling of the temperature-adjusted unit 31 can be prevented.Further, pressure loss in the refrigerant flow to the cooling system forthe temperature-adjusted unit 31, including the refrigerant passages 52,54, 55 and the cooling passage 32, can be reduced, enabling acorresponding reduction in an amount of power required to operate thecompressor 12 in order to circulate the refrigerant.

The temperature-adjusted unit 31 is, for example, an ATF cooler thatcools ATF used as lubricating oil and hydraulic working oil for atransaxle installed in a vehicle by performing heat exchange with theATF. The ATF is charged into the interior of the transaxle, not shown inthe drawings, in order to cool and lubricate respective constituentmembers of the transaxle. For this purpose, the ATF flows to thetemperature-adjusted unit 31 from the transaxle through a pipe, notshown in the drawings, exchanges heat with the refrigerant in thetemperature-adjusted unit 31, and then returns to the transaxle througha pipe, not shown in the drawing.

The heat exchanger 18 is disposed inside a duct 40 through which airflows. The heat exchanger 18 adjusts a temperature of air-conditioningair flowing through the duct 40 by performing heat exchange between therefrigerant and the air-conditioning air. The duct 40 includes a ductinlet 41, which is an inlet through which the air-conditioning air flowsinto the duct 40, and a duct outlet 42, which is an outlet through whichthe air-conditioning air flows out of the duct 40. A fan 43 is disposedinside the duct 40 in the vicinity of the duct inlet 41.

When the fan 43 is driven, air flows through the duct 40. When the fan43 is operative, the air-conditioning air flows into the interior of theduct 40 through the duct inlet 41. The air flowing into the duct 40 maybe outside air or air in a passenger compartment of the vehicle. Anarrow 45 in FIG. 1 indicates a flow of the air-conditioning air thatflows through the heat exchanger 18 so as to exchange heat with therefrigerant of the vapor compression refrigeration cycle 10. In the heatexchanger 18 during a cooling operation, the air-conditioning air iscooled while the refrigerant receives heat transfer from theair-conditioning air so as to be heated. In the heat exchanger 18 duringa heating operation, the air-conditioning air is heated while therefrigerant transfers heat to the air-conditioning air so as to becooled. An arrow 46 indicates a flow of the air-conditioning air flowingout of the duct 40 through the duct outlet 42 after being subjected totemperature adjustment in the heat exchanger 18.

During the cooling operation, the refrigerant flows through the vaporcompression refrigeration cycle 10 so as to pass sequentially through apoint A, a point B, a point C, a point D, and a point E, as shown inFIG. 1. Thus, the refrigerant circulates between the compressor 12, theheat exchanger 14, the expansion valve 16, and the heat exchanger 18.The refrigerant circulates within the vapor compression refrigerationcycle 10 through a refrigerant circulation passage formed by connectingthe compressor 12, the heat exchanger 14, the expansion valve 16, andthe heat exchanger 18 in sequence using the refrigerant passages 21 to26.

FIG. 2 is a Mollier chart showing states of the refrigerant during thecooling operation of the vapor compression refrigeration cycle 10according to the first embodiment. An abscissa in FIG. 2 shows aspecific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinateshows an absolute pressure (unit: MPa) of the refrigerant. A curve inthe diagram is a saturation vapor line and a saturation liquid line ofthe refrigerant. FIG. 2 shows a thermodynamic state of the refrigerantat each point (i.e. the points A, B, C, D, and E) of the vaporcompression refrigeration cycle 10, in which the refrigerant flows fromthe compressor 12 into the refrigerant passage 23 via the heat exchanger14, cools the temperature-adjusted unit 31, returns to the refrigerantpassage 23, and then returns to the compressor 12 via the expansionvalve 16 and the heat exchanger 18.

As shown in FIG. 2, the refrigerant (point A) that is aspirated into thecompressor 12 in a superheated vapor state is adiabatically compressedin the compressor 12 along a geometric entropy line. As the refrigerantis compressed, the pressure and temperature thereof rise such that therefrigerant turns into high-temperature, high-pressure, highlysuperheated vapor (point B). The refrigerant then flows to the heatexchanger 14.

The high-pressure refrigerant vapor that flows into the heat exchanger14 exchanges heat with outside air in the heat exchanger 14 and iscooled thereby. As a result, the refrigerant changes from superheatedvapor into dry saturated vapor while remaining at a constant pressure.Latent heat of condensation is discharged such that the refrigerantgradually liquefies, thereby turning into wet vapor in a gas-liquidmixed state, and when the refrigerant is condensed entirely, a saturatedliquid is formed. Further, sensible heat is discharged such that asupercooled liquid is formed (point C). The heat exchanger 14 forms arefrigerant liquid by isobarically discharging the heat of thesuperheated refrigerant gas compressed in the compressor 12 to anexternal medium. A gas phase refrigerant discharged from the compressor12 is condensed (liquefied) by discharging the heat thereof to theperiphery of the heat exchanger 14 such that the refrigerant is cooled.As a result of the heat exchange performed in the heat exchanger 14, thetemperature of the refrigerant falls such that the refrigerantliquefies.

The high-pressure liquid phase refrigerant liquefied by the heatexchanger 14 flows to the heat exchange unit 30 through the refrigerantpassage 52, the open/close valve 53, and the refrigerant passage 54, inthat order, and cools the temperature-adjusted unit 31. As a result ofthe heat exchange performed with the temperature-adjusted unit 31, adegree of supercooling of the refrigerant decreases. More specifically,the temperature of the refrigerant in the supercooled liquid state risesupon reception of sensible heat from the temperature-adjusted unit 31 soas to approach a liquid refrigerant saturation temperature, whereby therefrigerant is heated to a temperature slightly below the saturationtemperature (point D). Next, the refrigerant flows into the expansionvalve 16 through the refrigerant passage 23. By passing through theexpansion valve 16, the refrigerant in the supercooled liquid state isthrottle-expanded such that the temperature and pressure of therefrigerant fall while the specific enthalpy thereof remains unchanged.As a result, the refrigerant turns into low-temperature, low-pressurewet vapor in a gas-liquid mixed state (point E).

The wet vapor state refrigerant discharged from the expansion valve 16flows into the heat exchanger 18 through the refrigerant passage 24. Thewet vapor state refrigerant flows into the tube of the heat exchanger18. While flowing through the tube of the heat exchanger 18, therefrigerant absorbs heat from the air-conditioning via the fin as latentheat of evaporation, and as a result, the refrigerant evaporates whileremaining at a constant pressure. When the refrigerant turns entirelyinto dry saturated vapor, the temperature of the refrigerant vapor israised further by sensible heat, and as a result, superheated vapor isformed (point A). In the heat exchanger 18, the refrigerant absorbsperipheral heat so as to be heated. The vaporized refrigerant then flowsinto the four-way valve 13 through the refrigerant passage 25, and isthen aspirated into the compressor 12 via the refrigerant passage 26.The compressor 12 compresses the refrigerant flowing from the heatexchanger 18. In accordance with this cycle, the refrigerant undergoesseveral changes of state, namely compression, condensation, throttleexpansion, and evaporation, repeatedly and continuously.

Note that a theoretical refrigeration cycle was described in the abovedescription of the vapor compression refrigeration cycle. Needless tomention, however, in the actual vapor compression refrigeration cycle10, loss in the compressor 12 and pressure loss and heat loss in therefrigerant must be taken into account.

During the cooling operation, the heat exchanger 18 absorbs heat fromperipheral air introduced so as to contact the heat exchanger 18 as themist-form refrigerant flowing through the interior of the heat exchanger18 vaporizes. The heat exchanger 18 uses the low-temperature,low-pressure refrigerant throttle-expanded and reduced in pressure bythe expansion valve 16 to cool the passenger compartment of the vehicleby absorbing vaporization heat generated when the wet vapor of therefrigerant evaporates into a refrigerant gas from the air-conditioningair that flows into the passenger compartment of the vehicle. Theair-conditioning air reduced in temperature when the heat thereof isabsorbed by the heat exchanger 18 flows into the passenger compartmentof the vehicle, and as a result, the passenger compartment of thevehicle is cooled.

While the vapor compression refrigeration cycle 10 is operative, therefrigerant cools the passenger compartment by absorbing vaporizationheat from the air in the passenger compartment of the vehicle in theheat exchanger 18. In addition, the high-pressure liquid refrigerantdischarged from the heat exchanger 14 flows into the heat exchange unit30 and cools the temperature-adjusted unit 31 by exchanging heat withthe temperature-adjusted unit 31. Therefore, the heat exchange apparatus1 cools the temperature-adjusted unit 31 installed in the vehicle usingthe vapor compression refrigeration cycle 10 for air-conditioning thepassenger compartment of the vehicle. Note that a temperature to whichthe temperature-adjusted unit 31 is to be cooled is preferably at leastlower than an upper limit value of a target temperature range serving asa temperature range of the temperature-adjusted unit 31.

Returning to FIG. 1, the heat exchange apparatus 1 includes a flowcontrol valve 51. The flow control valve 51 is disposed in therefrigerant passage 23 a forming a part of the refrigerant passage 23between the heat exchanger 14 and the expansion valve 16. The pressureloss of the refrigerant flowing through the refrigerant passage 23 a isincreased or reduced by varying a valve opening of the flow controlvalve 51, and as a result, the flow control valve 51 adjusts a flow rateof the refrigerant flowing through the refrigerant passage 23 a and aflow rate of the refrigerant flowing through the refrigerant passages52, 54, 55 and the cooling passage 32 as desired.

For example, when the flow control valve 51 is fully closed such thatthe valve opening thereof is set at 0%, all of the refrigerant flowingbetween the heat exchanger 14 and the expansion valve 16 flows into therefrigerant passages 52, 54, 55 and the cooling passage 32. When thevalve opening of the flow control valve 51 is increased, the flow rateof the refrigerant flowing through the refrigerant passage 23 a, of therefrigerant flowing between the heat exchanger 14 and the expansionvalve 16, increases while the flow rate of the refrigerant flowingthrough the refrigerant passages 52, 54, 55 and the cooling passage 32in order to cool the temperature-adjusted unit 31 decreases. When thevalve opening of the flow control valve 51 is reduced, the flow rate ofthe refrigerant flowing through the refrigerant passage 23 a, of therefrigerant flowing between the heat exchanger 14 and the expansionvalve 16, decreases while the flow rate of the refrigerant flowingthrough the refrigerant passages 52, 54, 55 and the cooling passage 32in order to cool the temperature-adjusted unit 31 increases.

When the valve opening of the flow control valve 51 is increased, theflow rate of the refrigerant that cools the temperature-adjusted unit 31decreases, leading to a reduction in the ability to cool thetemperature-adjusted unit 31. When the valve opening of the flow controlvalve 51 is reduced, the flow rate of the refrigerant that cools thetemperature-adjusted unit 31 increases, leading to an improvement in theability to cool the temperature-adjusted unit 31. The amount ofrefrigerant that flows to the heat exchange unit 30 can be adjusted toan optimum amount using the flow control valve 51, and thereforeovercooling of the temperature-adjusted unit 31 can be preventedreliably. Moreover, pressure loss in the flow of refrigerant through therefrigerant passages 52, 54, 55 and the cooling passage 32 and the powerconsumption of the compressor 12 required to circulate the refrigerantcan be reliably reduced.

An example of control performed to adjust the valve opening of the flowcontrol valve 51 will now be described. FIGS. 3A to 3D are schematicviews showing opening control of the flow control valve 51. An abscissaof graphs shown in FIGS. 3A to 3D shows time. An ordinate of the graphin FIG. 3A shows the valve opening in a case where the flow controlvalve 51 is an electric expansion valve using a stepping motor. Anordinate of the graph in FIG. 3B shows the valve opening in a case wherethe flow control valve 51 is a temperature expansion valve that isoperated to open and close in response to temperature variation. Anordinate of the graph in FIG. 3C shows the temperature of thetemperature-adjusted unit 31. An ordinate of the graph in FIG. 3D showsa temperature difference between an outlet and an inlet of thetemperature-adjusted unit 31.

The temperature-adjusted unit 31 is cooled as the refrigerant passesthrough the heat exchange unit 30. The opening of the flow control valve51 is adjusted by monitoring the temperature of the temperature-adjustedunit 31 or the temperature difference between an outlet temperature andan inlet temperature of the temperature-adjusted unit 31, for example.Referring to the graph in FIG. 3C, for example, the temperature of thetemperature-adjusted unit 31 is monitored by providing a temperaturesensor that continuously measures the temperature of thetemperature-adjusted unit 31. Further, referring to the graph in FIG.3D, for example, the temperature difference between the outlet and theinlet of the temperature-adjusted unit 31 is monitored by providing atemperature sensor that measures the inlet temperature and the outlettemperature of the temperature-adjusted unit 31.

When the temperature of the temperature-adjusted unit 31 exceeds atarget temperature or the outlet/inlet temperature difference of thetemperature-adjusted unit 31 exceeds a target temperature difference (3to 5° C., for example), the opening of the flow control valve 51 isreduced, as shown on the graphs in FIGS. 3A and 3B. As described above,when the opening of the flow control valve 51 is narrowed, the flow rateof the refrigerant flowing to the heat exchange unit 30 increases, andtherefore the temperature-adjusted unit 31 can be cooled moreeffectively. As a result, the temperature of the temperature-adjustedunit 31 can be reduced to or below the target temperature, as shown onthe graph in FIG. 3C, or the outlet/inlet temperature difference of thetemperature-adjusted unit 31 can be reduced to or below the targettemperature difference, as shown on the graph in FIG. 3D.

By adjusting the valve opening of the flow control valve 51 optimally inthis manner, an amount of refrigerant for obtaining a radiation capacityrequired to keep the temperature-adjusted unit 31 in an appropriatetemperature range can be secured, and as a result, thetemperature-adjusted unit 31 can be cooled appropriately. Hence,situations in which the temperature-adjusted unit 31 is damaged throughoverheating can be suppressed reliably.

FIG. 4 is a schematic view showing the heat exchange apparatus 1 in acondition where the four-way valve 13 has been switched. Comparing FIGS.1 and 4, the four-way valve 13 has been rotated 90°, thereby switchingthe path along which the refrigerant flowing into the four-way valve 13from the outlet of the compressor 12 is discharged from the four-wayvalve 13. During the cooling operation shown in FIG. 1, the refrigerantcompressed by the compressor 12 flows from the compressor 12 toward theheat exchanger 14. During the heating operation shown in FIG. 4, on theother hand, the refrigerant compressed by the compressor 12 flows fromthe compressor 12 toward the heat exchanger 18.

During the heating operation, the refrigerant flows through the vaporcompression refrigeration cycle 10 so as to pass sequentially through apoint A, a point B, a point E, a point D, and a point C, as shown inFIG. 4. Thus, the refrigerant circulates between the compressor 12, theheat exchanger 18, the expansion valve 16, and the heat exchanger 14.The refrigerant circulates within the vapor compression refrigerationcycle 10 through a refrigerant circulation passage formed by connectingthe compressor 12, the heat exchanger 18, the expansion valve 16, andthe heat exchanger 14 in sequence using the refrigerant passages 21 to26.

FIG. 5 is a Mollier chart showing states of the refrigerant during theheating operation of the vapor compression refrigeration cycle 10according to the first embodiment. An abscissa in FIG. 5 shows thespecific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinateshows the absolute pressure (unit: MPa) of the refrigerant. A curve inthe diagram is a saturation vapor line and a saturation liquid line ofthe refrigerant. FIG. 5 shows a thermodynamic state of the refrigerantat each point (i.e. the points A, B, E, D, and C) of the vaporcompression refrigeration cycle 10, in which the refrigerant flows fromthe compressor 12 into the refrigerant passage 23 via the heat exchanger18 and the expansion valve 16, cools the temperature-adjusted unit 31,returns to the refrigerant passage 23, and then returns to thecompressor 12 via the heat exchanger 14.

As shown in FIG. 5, the refrigerant (point A) that is aspirated into thecompressor 12 in a superheated vapor state is adiabatically compressedin the compressor 12 along a geometric entropy line. As the refrigerantis compressed, the pressure and temperature thereof rise such that therefrigerant turns into high-temperature, high-pressure, highlysuperheated vapor (point B). The refrigerant then flows to the heatexchanger 18.

The high-pressure refrigerant vapor that flows into the heat exchanger18 is cooled in the heat exchanger 18 so as to change from superheatedvapor into dry saturated vapor while remaining at a constant pressure.Latent heat of condensation is discharged such that the refrigerantgradually liquefies, thereby turning into wet vapor in a gas-liquidmixed state, and when the refrigerant is condensed entirely, a saturatedliquid is formed. Further, sensible heat is discharged such that asupercooled liquid is formed (point E). The heat exchanger 18 forms arefrigerant liquid by isobarically discharging the heat of thesuperheated refrigerant gas compressed in the compressor 12 to anexternal medium. The gas phase refrigerant discharged from thecompressor 12 is condensed (liquefied) by discharging the heat thereofto the periphery of the heat exchanger 18 such that the refrigerant iscooled. As a result of the heat exchange performed in the heat exchanger18, the temperature of the refrigerant falls such that the refrigerantliquefies. Thus, the refrigerant is cooled by radiating the heat thereofto the periphery of the heat exchanger 18.

The high-pressure liquid phase refrigerant liquefied by the heatexchanger 18 flows into the expansion valve 16 through the refrigerantpassage 24. In the expansion valve 16, the supercooled liquid staterefrigerant is throttle-expanded such that the temperature and pressureof the refrigerant fall while the specific enthalpy thereof remainsunchanged, and as a result, low-temperature, low-pressure wet vapor in agas-liquid mixed state is formed (point D). The refrigerant reduced intemperature by the expansion valve 16 flows into the cooling passage 32of the heat exchange unit 30 through the refrigerant passages 23, 55 andcools the temperature-adjusted unit 31. As a result of the heat exchangeperformed with the temperature-adjusted unit 31, the refrigerant isheated such that a dryness of the refrigerant increases. When therefrigerant receives latent heat from the temperature-adjusted unit 31,a part thereof vaporizes, leading to an increase in a proportion ofsaturated vapor in the wet vapor state refrigerant (point C).

The wet vapor state refrigerant discharged from the heat exchange unit30 returns to the refrigerant passage 23 through the refrigerantpassages 54, 52, and then flows into the heat exchanger 14. The wetvapor state refrigerant flows into the tube of the heat exchanger 14.While flowing through the tube, the refrigerant absorbs heat from theoutside air via the fin as latent heat of evaporation, and as a result,the refrigerant evaporates while remaining at a constant pressure. Whenthe refrigerant turns entirely into dry saturated vapor, the temperatureof the refrigerant vapor is raised further by sensible heat, and as aresult, the refrigerant vapor turns into superheated vapor (point A).The vaporized refrigerant is aspirated into the compressor 12 via therefrigerant passage 22. The compressor 12 compresses the refrigerantflowing from the heat exchanger 14. In accordance with this cycle, therefrigerant undergoes several changes of state, namely compression,condensation, throttle expansion, and evaporation, repeatedly andcontinuously.

During the heating operation, the heat exchanger 18 adds heat to theperipheral air introduced so as to contact the heat exchanger 18 as therefrigerant vapor flowing through the interior thereof is condensed. Theheat exchanger 18 uses the high-temperature, high-pressure refrigerantadiabatically compressed by the compressor 12 to heat the passengercompartment of the vehicle by discharging condensation heat generatedwhen the refrigerant gas condenses into refrigerant wet vapor to theair-conditioning air that flows into the passenger compartment of thevehicle. The air-conditioning air increased in temperature afterreceiving heat from the heat exchanger 18 flows into the passengercompartment of the vehicle, and as a result, the passenger compartmentof the vehicle is heated.

In the heat exchange apparatus 1, a second passage and a refrigerantpassage 24 a serving as a fourth passage are connected in parallel andprovided on a path along which the refrigerant flows between theexpansion valve 16 and the heat exchanger 18. The refrigerant passage 24a forms a part of the refrigerant passage 24 forming the refrigerantpath between the expansion valve 16 and the heat exchanger 18. The heatexchange unit 30 is provided to be capable of exchanging heat with thefirst passage, as described above, and also provided in the secondpassage to be capable of exchanging heat with the second passage. Theheat exchange unit 30 is provided on the refrigerant path between theexpansion valve 16 and the heat exchanger 18. The heat exchange unit 30includes, in addition to the temperature-adjusted unit 31 and thecooling passage 32, a heating passage 33 constituted by a pipe throughwhich the refrigerant flows. The heat exchange apparatus 1 includes therefrigerant passage 24 a as a path that does not pass through the heatexchange unit 30, and includes refrigerant passages 62, 64, 65 and theheating passage 33 as a path that passes through the heat exchange unit30. The refrigerant path between the expansion valve 16 and the heatexchanger 18 bifurcates such that a part of the refrigerant flows to theheat exchange unit 30.

The refrigerant passages 62, 64, 65 are provided as a path along whichthe refrigerant flows to the heating passage 33. One end portion of theheating passage 33 is connected to the refrigerant passage 64, andanother end portion of the heating passage 33 is connected to therefrigerant passage 65. The refrigerant passage 62 and the refrigerantpassage 64 communicate via an open/close valve 63. The refrigerant flowsfrom the refrigerant passage 24 into the heating passage 33 througheither the refrigerant passages 62, 64 or the refrigerant passage 65.The refrigerant that flows through the heating passage 33 exchanges heatwith the temperature-adjusted unit 31, and then returns to therefrigerant passage 24 through the other of the refrigerant passages 62,64 and the refrigerant passage 65. The second passage connected to therefrigerant passage 24 a in parallel therewith includes the refrigerantpassages 62, 64 on the heat exchanger 18 side of the heat exchange unit30, the heating passage 33 provided in the heat exchange unit 30, andthe refrigerant passage 65 on the expansion valve 16 side of the heatexchange unit 30. The open/close valve 63 opens and closes the secondpassage.

FIG. 6 is a schematic view showing the heat exchange apparatus 1 whenthe temperature-adjusted unit 31 is heated. When thetemperature-adjusted unit 31 shown in FIGS. 1 and 4 is to be cooled, theopen/close valve 53 is opened and the open/close valve 63 is closed.When the open/close valve 53 is open, the open/close valve 63 is closed.Accordingly, the refrigerant flows through the cooling passage 32 butdoes not flow through the heating passage 33. Heat is transferred to therefrigerant flowing through the cooling passage 32 from thetemperature-adjusted unit 31, and as a result, the temperature-adjustedunit 31 is cooled. When the temperature-adjusted unit 31 shown in FIG. 6is to be heated, on the other hand, the open/close valve 63 is openedand the open/close valve 53 is closed. When the open/close valve 53 isclosed, the open/close valve 63 is open. Accordingly, the refrigerantflows through the heating passage 33 but does not flow through thecooling passage 32. Heat is transferred from the refrigerant flowingthrough the heating passage 33 to the temperature-adjusted unit 31, andas a result, the temperature-adjusted unit 31 is heated.

As shown in FIG. 6, when the refrigerant flowing between the expansionvalve 16 and the heat exchanger 18 via the heating passage 33 flowsthrough the heating passage 33, heat is applied to thetemperature-adjusted unit 31, thereby raising the temperature of thetemperature-adjusted unit 31. The heat exchange unit 30 is structuredsuch that heat exchange can be performed between thetemperature-adjusted unit 31 and the refrigerant in the heating passage33. Similarly to the disposition of the temperature-adjusted unit 31 inthe cooling passage 32, an outer peripheral surface of the heatingpassage 33 may contact the casing of the temperature-adjusted unit 31directly. Alternatively, a heat pipe may be disposed between thetemperature-adjusted unit 31 and the heating passage 33 such that theheating passage 33 is set as a heat pipe heating portion and thetemperature-adjusted unit 31 is set as a heat pipe cooling portion.Since the temperature-adjusted unit 31 is disposed on the exterior ofthe heating passage 33, pressure loss in the vapor compressionrefrigeration cycle 10 does not increase, and therefore thetemperature-adjusted unit 31 can be heated without increasing the powerof the compressor 12.

The refrigerant passages 62, 64, 65 and the heating passage 33 servingas the path that passes through the heat exchange unit 30 are providedin parallel with the refrigerant passage 24 a serving as the path thatdoes not pass through the heat exchange unit 30 as the path along whichthe refrigerant flows between the expansion valve 16 and the heatexchanger 18. A heating system for the temperature-adjusted unit 31,including the refrigerant passages 62, 64, 65, is connected in parallelwith the refrigerant passage 24 a. By providing the path of therefrigerant that flows between the heat expansion valve 16 and the heatexchanger 18 without passing through the heat exchange unit 30 inparallel with the path of the refrigerant that passes through the heatexchange unit 30 and causing only a part of the refrigerant to flow tothe refrigerant passages 62, 64, 65, only a part of the refrigerantflowing between the expansion valve 16 and the heat exchanger 18 iscaused to flow to the heat exchange unit 30.

A situation in which an amount of refrigerant required to heat thetemperature-adjusted unit 31 is caused to flow to the refrigerantpassages 62, 64, 65 such that all of the refrigerant flows to the heatexchange unit 30 does not occur in the heat exchange unit 30. Hence, thetemperature-adjusted unit 31 can be heated appropriately, andoverheating of the temperature-adjusted unit 31 can be prevented.Further, pressure loss in the refrigerant flow to the heating system forthe temperature-adjusted unit 31, including the refrigerant passages 62,64, 65 and the heating passage 33, can be reduced, enabling acorresponding reduction in the amount of power required to operate thecompressor 12 in order to circulate the refrigerant.

A flow control valve 61 is disposed in the refrigerant passage 24 a asanother flow control valve differing from the flow control valve 51.Similarly to the flow control valve 51 described above, the pressureloss of the refrigerant flowing through the refrigerant passage 24 a isincreased or reduced by varying a valve opening of the flow controlvalve 61, and as a result, the flow control valve 61 adjusts the flowrate of the refrigerant flowing through the refrigerant passage 24 a andthe flow rate of the refrigerant flowing through the refrigerantpassages 62, 64, 65 and the heating passage 33 as desired.

When the valve opening of the flow control valve 61 is increased, theflow rate of the refrigerant for heating the temperature-adjusted unit31 decreases, leading to a reduction in an ability to raise thetemperature of the temperature-adjusted unit 31. When the valve openingof the flow control valve 61 is reduced, the flow rate of therefrigerant used to heat the temperature-adjusted unit 31 increases,leading to improvement in the ability to raise the temperature of thetemperature-adjusted unit 31. Using the flow control valve 61, theamount of refrigerant flowing to the heat exchange unit 30 can beadjusted to an optimum amount, and therefore overheating of thetemperature-adjusted unit 31 can be prevented reliably. In addition,pressure loss in the refrigerant flow through the refrigerant passages62, 64, 65 and the heating passage 33 and the amount of power consumedby the compressor 12 to circulate the refrigerant can be reducedreliably.

Note that when the temperature-adjusted unit 31 is cooled, the flowcontrol valve 61 is maintained in a fully open condition while theopening of the flow control valve 51 is controlled as described withreference to FIG. 3. By closing the open/close valve 63, the refrigerantcan be reliably prevented from flowing into the heating passage 33, andby fully opening the flow control valve 61, pressure loss in therefrigerant flowing through the refrigerant passage 24 a can beminimized. When the temperature-adjusted unit 31 is heated, on the otherhand, the flow control valve 51 is maintained in a fully open conditionwhile the opening of the flow control valve 61 is controlled similarlyto the opening control of the flow control valve 51 described withreference to FIG. 3, i.e. such that the flow rate of the refrigerantflowing through the heating passage 33 in order to heat thetemperature-adjusted unit 31 can be maintained at an appropriate level.By closing the open/close valve 53, the refrigerant can be reliablyprevented from flowing into the cooling passage 32, and by fully openingthe flow control valve 51, pressure loss in the refrigerant flowingthrough the refrigerant passage 23 a can be minimized.

FIG. 7 is a Mollier chart showing states of the refrigerant used in thevapor compression refrigeration cycle 10 according to the firstembodiment when the temperature-adjusted unit 31 is heated. An abscissain FIG. 7 shows a specific enthalpy (unit: kJ/kg) of the refrigerant,while an ordinate shows an absolute pressure (unit: MPa) of therefrigerant. A curve in the diagram is a saturation vapor line and asaturation liquid line of the refrigerant. FIG. 7 shows a thermodynamicstate of the refrigerant at each point (i.e. the points A, B, E, F, andD) of the vapor compression refrigeration cycle 10, in which therefrigerant flows from the compressor 12 into the refrigerant passage 24via the heat exchanger 18, heats the temperature-adjusted unit 31,returns to the refrigerant passage 24, and then returns to thecompressor 12 via the expansion valve 16 and the heat exchanger 14.

As shown in FIG. 7, the refrigerant (point A) that is aspirated into thecompressor 12 in a superheated vapor state is adiabatically compressedin the compressor 12 along a geometric entropy line. As the refrigerantis compressed, the pressure and temperature thereof rise such that therefrigerant turns into high-temperature, high-pressure, highlysuperheated vapor (point B). The refrigerant then flows to the heatexchanger 18.

The high-pressure refrigerant vapor that flows into the heat exchanger18 is cooled in the heat exchanger 18 so as to change from superheatedvapor into dry saturated vapor while remaining at a constant pressure.Latent heat of condensation is discharged such that the refrigerantgradually liquefies, thereby turning into wet vapor in a gas-liquid,mixed state (point E). The heat exchanger 18 forms a refrigerant liquidby isobarically discharging the heat of the superheated refrigerant gascompressed in the compressor 12 to an external medium. The gas phaserefrigerant discharged from the compressor 12 is condensed (liquefied)by discharging the heat thereof to the periphery of the heat exchanger18 such that the refrigerant is cooled. As a result of the heat exchangeperformed in the heat exchanger 18, the temperature of the refrigerantfalls such that the refrigerant liquefies. Thus, the refrigerant iscooled by radiating the heat thereof to the periphery of the heatexchanger 18.

The wet vapor state refrigerant flowing out of the heat exchanger 18flows into the heating passage 33 of the heat exchange unit 30 via therefrigerant passages 24, 62, 64 in order to heat thetemperature-adjusted unit 31. Having exchanged heat with thetemperature-adjusted unit 31, the refrigerant is cooled and condensed.When the refrigerant is condensed entirely in the heat exchange unit 30,the refrigerant forms a saturated liquid. Further, the refrigerantdischarges sensible heat so as to form a supercooled liquid (point F).

The high-pressure liquid phase refrigerant liquefied by the heatexchange unit 30 flows into the expansion valve 16 through therefrigerant passages 65, 24. In the expansion valve 16, the supercooledliquid state refrigerant is throttle-expanded such that the temperatureand pressure of the refrigerant fall while the specific enthalpy thereofremains unchanged. As a result, the refrigerant turns intolow-temperature, low-pressure wet vapor in a gas-liquid mixed state(point D).

The refrigerant lowered in temperature in the expansion valve 16 flowsinto the heat exchanger 14 through the refrigerant passage 23. The wetvapor state refrigerant flows into the tube of the heat exchanger 14.While flowing through the tube, the refrigerant absorbs heat from theoutside air via the fin as latent heat of evaporation, and as a result,the refrigerant evaporates while remaining at a constant pressure. Whenthe refrigerant turns entirely into dry saturated vapor, the temperatureof the refrigerant vapor is raised further by sensible heat, and as aresult, superheated vapor is formed (point A). The vaporized refrigerantis then aspirated into the compressor 12 via the refrigerant passage 22.The compressor 12 compresses the refrigerant flowing from the heatexchanger 14. In accordance with this cycle, the refrigerant undergoesseveral changes of state, namely compression, condensation, throttleexpansion, and evaporation, repeatedly and continuously.

If, as described with reference to FIGS. 4 and 5, low-temperaturerefrigerant is caused to flow to the cooling passage 32 of the heatexchange unit 30 in order to cool the temperature-adjusted unit 31during a heating operation performed in a cold period, thetemperature-adjusted unit 31 is cooled to an extremely low temperature.In a case where the temperature-adjusted unit 31 is an ATF cooler, theATF is preferably not cooled excessively so that fuel efficiencydeterioration can be suppressed and gear lubrication can be secured.Hence, when the ATF temperature is low, high-pressure refrigerant isintroduced into the heating passage 33 of the heat exchange unit 30 inorder to exchange heat with the temperature-adjusted unit 31, as shownin FIGS. 6 and 7, and as a result, the ATF can be actively heated. Sincethe temperature of the ATF can be raised to an appropriate level, aviscosity of the ATF does not increase, and therefore problems such asinsufficient gear lubrication and an increase in friction loss can beavoided. Further, the ATF can be warmed up quickly when the temperatureof the ATF is low, and as a result, a fuel efficiency can be improvedand gear lubrication can be secured.

As described above, the heat exchange apparatus 1 according to thisembodiment includes the vapor compression refrigeration cycle 10, whichis provided to cool and heat the passenger compartment of the vehicle byperforming heat exchange with the air-conditioning air in the hearexchanger 18. By switching a flow direction of the refrigerant throughthe vapor compression refrigeration cycle 10 between the coolingoperation and the heating operation using the four-way valve 13, thetemperature of the air-conditioning air flowing into the passengercompartment of the vehicle can be adjusted appropriately using thesingle heat exchanger 18 during both the cooling operation and theheating operation. Since there is no need to provide two heat exchangersto exchange heat with the air-conditioning air, reductions in both thecost and the size of the heat exchange apparatus 1 can be achieved.

During the cooling operation, the refrigerant has a temperature and apressure at the outlet of the expansion valve 16 required originally tocool the passenger compartment of the vehicle. A radiation capacity ofthe heat exchanger 14 is determined such that the refrigerant can becooled sufficiently. When the refrigerant is used to cool thetemperature-adjusted unit 31 after passing through the expansion valve16, an ability of the heat exchanger 18 to cool the air-conditioning airdeteriorates, leading to a reduction in a passenger compartment coolingability. With the heat exchange apparatus 1 according to thisembodiment, on the other hand, the refrigerant is cooled to asufficiently supercooled state in the heat exchanger 14, and thehigh-pressure refrigerant at the outlet of the heat exchanger 14 is usedto cool the temperature-adjusted unit 31. Therefore, thetemperature-adjusted unit 31 can be cooled without affecting the abilityto cool the air in the passenger compartment.

Specifications of the heat exchanger 14 (more specifically, a size or aheat exchange performance of the heat exchanger 14) are determined suchthat the temperature of the liquid phase refrigerant after passingthrough the heat exchanger 14 is lower than a temperature required tocool the passenger compartment. The specifications of the heat exchanger14 are determined such that the heat exchanger 14 has a radiationcapacity which is greater than that of a heat exchanger of a vaporcompression refrigeration cycle used in a case where thetemperature-adjusted unit 31 is not cooled by an amount of heat assumedto be received by the refrigerant from the temperature-adjusted unit 31.The heat exchange apparatus 1 including the heat exchanger 14 havingthese specifications can cool the temperature-adjusted unit 31appropriately while maintaining a superior cooling performance withrespect to the passenger compartment of the vehicle and withoutincreasing the power of the compressor 12.

During the heating operation, the refrigerant is heated in the heatexchange unit 30 by heat absorbed from the temperature-adjusted unit 31,and heated further in the heat exchanger 14 by heat absorbed from theoutside air. When the refrigerant is heated by both the heat exchangeunit 30 and the heat exchanger 14, the refrigerant can be heated to asufficient superheated vapor state at the outlet of the heat exchanger14, and therefore the temperature-adjusted unit 31 can be cooledappropriately while maintaining a superior heating performance withrespect to the passenger compartment of the vehicle. Since therefrigerant is heated by the heat exchange unit 30 and waste heat fromthe temperature-adjusted unit 31 is used effectively to heat thepassenger compartment, an improvement can be achieved in a coefficientof performance, leading to a reduction in an amount of power consumed tocompress the refrigerant adiabatically in the compressor 12 during theheating operation.

Furthermore, during a heating operation performed in a cold period, thehigh-temperature, high-pressure refrigerant pressurized by thecompressor 12 is used to heat the air-conditioning air and thetemperature-adjusted unit 31. During the heating operation, thetemperature of the temperature-adjusted unit 31 may be measured by athermistor or the like such that when the temperature of thetemperature-adjusted unit 31 is high, the temperature-adjusted unit 31can be cooled by opening the open/close valve 53 and closing theopen/close valve 63, and when the temperature of thetemperature-adjusted unit 31 is low, the temperature-adjusted unit 31can be heated by opening the open/close valve 63 and closing theopen/close valve 53. The temperature-adjusted unit 31 is disposed sothat it can be cooled by the refrigerant flowing through the coolingpassage 32 and heated by the refrigerant flowing through the heatingpassage 33, and the refrigerant flow through the cooling passage 32 andthe heating passage 33 is switched by opening and closing the open/closevalves 53, 63. Hence, the temperature-adjusted unit 31 can be cooled orheated freely using a simple configuration and simple control, and as aresult, the temperature of the temperature-adjusted unit 31 can beadjusted to an optimum level easily.

In the heat exchange apparatus 1, the temperature-adjusted unit 31 iscooled and heated using the vapor compression refrigeration cycle 10.Therefore, a dedicated cooling device such as a water circulation pumpor a cooling fan is not required to cool the temperature-adjusted unit31, and a dedicated heating device such as a heater is not required toheat the temperature-adjusted unit 31. Accordingly, a number ofconfigurations required to adjust the temperature of thetemperature-adjusted unit 31 can be reduced, enabling simplification ofthe apparatus configuration, and as a result, a manufacturing cost ofthe heat exchange apparatus 1 can be reduced. Furthermore, there is noneed to operate a power source of a pump, a cooling fan, a heater, orthe like for adjusting the temperature of the temperature-adjusted unit31, and therefore no power need be consumed to operate such a powersource. As a result, a reduction can be achieved in the amount of powerconsumed to heat and cool the temperature-adjusted unit 31.

FIG. 8 is a schematic view showing a configuration of the heat exchangeapparatus 1 according to a second embodiment. The heat exchangeapparatus 1 according to the second embodiment differs from that of thefirst embodiment in that a heat exchanger 15 serving as a third heatexchanger is disposed on the refrigerant path between the heat exchangeunit 30 and the expansion valve 16.

By providing the heat exchanger 15, the refrigerant path between theheat exchanger 14 and the expansion valve 16 is divided into therefrigerant passage 23 on the heat exchanger 14 side of the heatexchanger 15 and a refrigerant passage 27 on the expansion valve 16 sideof the heat exchanger 15. The refrigerant passage 23 is provided as apath for the refrigerant flowing between the heat exchanger 14 and theheat exchanger 15. The first passage serving as the cooling system forthe temperature-adjusted unit 31, which includes the cooling passage 32,is connected in parallel with the refrigerant passage 23 a forming apart of the refrigerant passage 23.

During the cooling operation, the refrigerant flows through the vaporcompression refrigeration cycle 10 so as to pass sequentially through apoint A, a point B, a point C, a point D, a point G, and a point E, asshown in FIG. 8. Thus, the refrigerant circulates between the compressor12, the heat exchangers 14, 15, the expansion valve 16, and the heatexchanger 18. The refrigerant circulates within the vapor compressionrefrigeration cycle 10 through a refrigerant circulation passage formedby connecting the compressor 12, the heat exchangers 14, 15, theexpansion valve 16, and the heat exchanger 18 in sequence using therefrigerant passages 21 to 27.

FIG. 9 is a Mollier chart showing states of the refrigerant during thecooling operation of the vapor compression refrigeration cycle 10according to the second embodiment. An abscissa in FIG. 9 shows thespecific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinateshows the absolute pressure (unit: MPa) of the refrigerant. A curve inthe diagram is a saturation vapor line and a saturation liquid line ofthe refrigerant. FIG. 9 shows the thermodynamic state of the refrigerantat each point (i.e. the points A, B, C, D, G, and E) of the vaporcompression refrigeration cycle 10, in which the refrigerant flows fromthe compressor 12 into the refrigerant passage 23 via the heat exchanger14, cools the temperature-adjusted unit 31, returns to the refrigerantpassage 23, flows into the refrigerant passage 27 via the heat exchanger15, and then returns to the compressor 12 via the expansion valve 16 andthe heat exchanger 18.

The vapor compression refrigeration cycle 10 according to the secondembodiment is identical to that of the first embodiment except for asystem extending from the heat exchanger 14 to the expansion valve 16.More specifically, the refrigerant states from the point D to the pointB via the points E and A on the Mollier chart shown in FIG. 2 areidentical to the refrigerant states from the point G to the point B viathe points E and A on the Mollier chart shown in FIG. 9. Therefore,refrigerant states from the point B to the point G, which are unique tothe vapor compression refrigeration cycle 10 according to the secondembodiment, will be described below.

The refrigerant (point B) adiabatically compressed intohigh-temperature, high-pressure superheated vapor by the compressor 12is cooled in the heat exchanger 14. As a result, the refrigerantdischarges sensible heat while remaining at a constant pressure so as tochange from superheated vapor into dry saturated vapor. Latent heat ofcondensation is then discharged such that the refrigerant graduallyliquefies, thereby turning into wet vapor in a gas-liquid mixed state,and when the refrigerant is condensed entirely, it turns into asaturated liquid (point C).

The saturated liquid state refrigerant that flows out of the heatexchanger 14 flows into the heat exchange unit 30 through therefrigerant passages 52, 54. In the heat exchange unit 30, heat isdischarged to the liquid refrigerant condensed while passing through theheat exchanger 14, whereby the temperature-adjusted unit 31 is cooled.The refrigerant is heated by the heat exchange performed with thetemperature-adjusted unit 31, and as a result, the dryness of therefrigerant increases. When the refrigerant receives latent heat fromthe temperature-adjusted unit 31 so as to undergo partial vaporization,the refrigerant turns into wet vapor intermixing saturated liquid andsaturated vapor (point D).

The refrigerant then flows into the heat exchanger 15. The wet vapor ofthe refrigerant exchanges heat with the outside air in the heatexchanger 15 so as to be condensed again, and when condensed entirely,the refrigerant forms a saturated liquid. Further, the refrigerantdischarges sensible heat so as to form a supercooled liquid (point G).The refrigerant then passes through the expansion valve 16 so as to formlow-temperature, low-pressure wet vapor (point E).

In the vapor compression refrigeration cycle 10, the high-pressurerefrigerant discharged from the compressor 12 is condensed by both theheat exchanger 14 and the heat exchanger 15. When the refrigerant iscooled sufficiently in the heat exchanger 15, the refrigerant has thetemperature and pressure originally required to cool the passengercompartment of the vehicle at the outlet of the expansion valve 16.Accordingly, the amount of heat received by the refrigerant from theoutside while evaporating in the heat exchanger 18 can be madesufficiently large. By determining the radiation capacity of the heatexchanger 15 so that the refrigerant can be cooled sufficiently in thismanner, the temperature-adjusted unit 31 can be cooled without affectingthe ability to cool the air in the passenger compartment. As a result,both the ability to cool the temperature-adjusted unit 31 and theability to cool the passenger compartment can be secured reliably.

In the vapor compression refrigeration cycle 10 according to the firstembodiment, the heat exchanger 14 is disposed between the compressor 12and the expansion valve 16 such that during the cooling operation, anamount of heat exchange corresponding to cooling of the passengercompartment and cooling of the temperature-adjusted unit 31 must beperformed by the heat exchanger 14. Accordingly, the refrigerant must becooled further from the saturated liquid state in the heat exchanger 14until the refrigerant exhibits a predetermined degree of supercooling.When the refrigerant in the supercooled liquid state is cooled, thetemperature of the refrigerant approaches an atmospheric temperature,leading to a reduction in a cooling efficiency of the refrigerant, andtherefore a capacity of the heat exchanger 14 must be increased. As aresult, a size of the heat exchanger 14 increases, which isdisadvantageous for the vehicle-installed heat exchange apparatus 1.When the size of the heat exchanger 14 is reduced to facilitate vehicleinstallation, on the other hand, the radiation capacity of the heatexchanger 14 deteriorates. As a result, it may be impossible to reducethe temperature of the refrigerant at the outlet of the expansion valve16 sufficiently, leading to a deficiency in the ability to cool thepassenger compartment.

With the vapor compression refrigeration cycle 10 according to thesecond embodiment, however, the heat exchangers 14, 15 are disposed intwo stages between the compressor 12 and the expansion valve 16, and theheat exchange unit 30 serving as the cooling system for thetemperature-adjusted unit 31 is provided between the heat exchanger 14and the heat exchanger 15. As shown in FIG. 9, the refrigerant need onlybe cooled to a saturated liquid state in the heat exchanger 14. The wetvapor state refrigerant that is partially vaporized after receivinglatent heat of evaporation from the temperature-adjusted unit 31 is thencooled again in the heat exchanger 15. The state of the refrigerant ischanged at a constant temperature until the wet vapor state refrigeranthas been completely condensed into a saturated liquid. Furthermore, theheat exchanger 15 cools the refrigerant to a degree of supercoolingrequired to cool the passenger compartment of the vehicle. Therefore, incomparison with the first embodiment, there is no need to increase thedegree of supercooling of the refrigerant, and the capacity of the heatexchangers 14, 15 can be reduced accordingly. Hence, the ability to coolthe passenger compartment can be secured, and the size of the heatexchangers 14, 15 can be reduced. As a result, the heat exchangeapparatus 1 obtained herein is small enough to be suitable forinstallation in a vehicle.

When the refrigerant flowing into the heat exchange unit 30 from theheat exchanger 14 cools the temperature-adjusted unit 31, therefrigerant is heated by heat received from the temperature-adjustedunit 31. When the refrigerant is heated to or above a vapor saturationtemperature in the heat exchange unit 30 such that the refrigerantvaporizes entirely, an amount of heat exchange between the refrigerantand the temperature-adjusted unit 31 decreases so that thetemperature-adjusted unit 31 can no longer be cooled efficiently andpressure loss occurring in the refrigerant while flowing through pipesincreases. Therefore, the refrigerant is preferably cooled sufficientlyin the heat exchanger 14 to ensure that the refrigerant does notvaporize entirely after cooling the temperature-adjusted unit 31.

More specifically, the state of the refrigerant at the outlet of theheat exchanger 14 is caused to approach a saturated liquid such thattypically, the state of the refrigerant exists on the saturation liquidline at the outlet of the heat exchanger 14. When the heat exchanger 14is provided with the ability to cool the refrigerant sufficiently inthis manner, the radiation capacity of the heat exchanger 14 fordischarging heat from the refrigerant improves beyond the radiationcapacity of the heat exchanger 15. By cooling the refrigerantsufficiently in the heat exchanger 14 having a relatively largeradiation capacity, the refrigerant can be kept in the wet vapor stateafter receiving heat from the temperature-adjusted unit 31, therebyavoiding a reduction in the amount of heat exchange between therefrigerant and the temperature-adjusted unit 31, and as a result, thetemperature-adjusted unit 31 can be cooled efficiently and sufficiently.After cooling the temperature-adjusted unit 31, the wet vapor staterefrigerant is efficiently cooled again in the heat exchanger 15 to asupercooled liquid state slightly below the saturation temperature.Hence, with the heat exchange apparatus 1 provided herein, both theability to cool the passenger compartment and the ability to cool thetemperature-adjusted unit 31 can be secured.

FIG. 10 is a schematic view showing the heat exchange apparatus 1according to the second embodiment in a condition where the four-wayvalve 13 has been switched. Comparing FIGS. 8 and 10, the four-way valve13 has been rotated 90°, thereby switching the path along which therefrigerant flowing into the four-way valve 13 from the outlet of thecompressor 12 is discharged from the four-way valve 13. During thecooling operation shown in FIG. 8, the refrigerant compressed by thecompressor 12 flows from the compressor 12 toward the heat exchanger 14.During the heating operation shown in FIG. 10, on the other hand, therefrigerant compressed by the compressor 12 flows from the compressor 12toward the heat exchanger 18.

During the heating operation, the refrigerant flows through the vaporcompression refrigeration cycle 10 so as to pass sequentially through apoint A, a point B, a point E, a point G, a point D, and a point C, asshown in FIG. 10. Thus, the refrigerant circulates between thecompressor 12, the heat exchanger 18, the expansion valve 16, and theheat exchangers 15, 14. The refrigerant circulates within the vaporcompression refrigeration cycle 10 through a refrigerant circulationpassage formed by connecting the compressor 12, the heat exchanger 18,the expansion valve 16, and the heat exchangers 15, 14 in sequence usingthe refrigerant passages 21 to 27.

FIG. 11 is a Mollier chart showing states of the refrigerant during theheating operation of the vapor compression refrigeration cycle 10according to the second embodiment. An abscissa in FIG. 11 shows thespecific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinateshows the absolute pressure (unit: MPa) of the refrigerant. A curve inthe diagram is a saturation vapor line and a saturation liquid line ofthe refrigerant. FIG. 11 shows the thermodynamic state of therefrigerant at each point (i.e. the points A, B, E, G, D, and C) of thevapor compression refrigeration cycle 10, in which the refrigerant flowsfrom the compressor 12 into the refrigerant passage 23 via the heatexchanger 18, the expansion valve 16, and the heat exchanger 15, coolsthe temperature-adjusted unit 31, returns to the refrigerant passage 23,and then returns to the compressor 12 via the heat exchanger 14.

The vapor compression refrigeration cycle 10 according to the secondembodiment is identical to that of the first embodiment except for asystem extending from the expansion valve 16 to the heat exchanger 14.More specifically, the refrigerant states from the point A to the pointD via the points B and E on the Mollier chart shown in FIG. 5 areidentical to the refrigerant states from the point A to the point G viathe points B and E on the Mollier chart shown in FIG. 11. Therefore,refrigerant states from the point G to the point A, which are unique tothe vapor compression refrigeration cycle 10 according to the secondembodiment, will be described below.

The refrigerant (point G) reduced in temperature by the expansion valve16 flows into the heat exchanger 15 through the refrigerant passage 27.The wet vapor state refrigerant flows into the tube of the heatexchanger 15. While flowing through the tube, the refrigerant absorbsheat from the outside air via the fin as latent heat of evaporation, andas a result, the refrigerant evaporates while remaining at a constantpressure. The refrigerant is then heated through heat exchange with theoutside air in the heat exchanger 15, whereby the dryness of therefrigerant increases. When the refrigerant receives the latent heat inthe heat exchanger 15, a part thereof vaporizes, leading to an increasein the proportion of saturated vapor in the wet vapor state refrigerant(point D).

The wet vapor state refrigerant discharged from the heat exchanger 15flows into the cooling passage 32 of the heat exchange unit 30 throughthe refrigerant passages 23, 55, and cools the temperature-adjusted unit31. In the heat exchange unit 30, heat is discharged to the wet vaporstate refrigerant intermixing saturated liquid and saturated vapor,whereby the temperature-adjusted unit 31 is cooled. The refrigerant isheated by the heat exchange performed with the temperature-adjusted unit31, and as a result, the dryness of the refrigerant increases. When therefrigerant receives latent heat from the temperature-adjusted unit 31,a part thereof vaporizes, leading to a further increase in theproportion of saturated vapor in the wet vapor state refrigerant (pointC).

The wet vapor state refrigerant discharged from the heat exchange unit30 returns to the refrigerant passage 23 through the refrigerantpassages 54, 52, and then flows into the heat exchanger 14. The wetvapor state refrigerant flows into the tube of the heat exchanger 14.While flowing through the tube, the refrigerant absorbs heat from theoutside air via the fin as latent heat of evaporation, and as a result,the refrigerant evaporates while remaining at a constant pressure. Whenthe refrigerant has turned entirely into dry saturated vapor, thetemperature of the refrigerant vapor is raised further by sensible heat,and as a result, the refrigerant vapor turns into superheated vapor(point A).

During the heating operation, the refrigerant is heated by heat absorbedfrom the outside air in the two heat exchangers 14, 15, and then heatedfurther by heat absorbed from the temperature-adjusted unit 31 in theheat exchange unit 30. By heating the refrigerant in both the heatexchange unit 30 and the heat exchangers 14, 15, the refrigerant can beheated to a sufficient superheated vapor state at the outlet of the heatexchanger 14, and therefore the temperature-adjusted unit 31 can becooled appropriately while maintaining a superior heating performancewith respect to the passenger compartment of the vehicle. Since therefrigerant is heated by the heat exchange unit 30 and waste heat fromthe temperature-adjusted unit 31 is used effectively to heat thepassenger compartment, the amount of power consumed to compress therefrigerant adiabatically in the compressor 12 during the heatingoperation can be reduced.

FIG. 12 is a schematic view showing the heat exchange apparatus 1 whenthe temperature-adjusted unit 31 according to the second embodiment isheated. Similarly to the first embodiment, by switching the open/closedconditions of the open/close valves 53, 63 such that the open/closevalve 53 is closed and the open/close valve 63 is open, a condition inwhich the refrigerant flows through the heating passage 33 but does notflow through the cooling passage 32 is established. At this time, heatis transferred to the temperature-adjusted unit 31 from the refrigerantflowing through the heating passage 33, and as a result, thetemperature-adjusted unit 31 is heated.

FIG. 13 is a Mollier chart showing states of the refrigerant used in thevapor compression refrigeration cycle 10 according to the secondembodiment when the temperature-adjusted unit 31 is heated. An abscissain FIG. 13 shows a specific enthalpy (unit: kJ/kg) of the refrigerant,while an ordinate shows an absolute pressure (unit: MPa) of therefrigerant. A curve in the diagram is a saturation vapor line and asaturation liquid line of the refrigerant. FIG. 13 shows a thermodynamicstate of the refrigerant at each point (i.e. the points A, B, E, F, andD) of the vapor compression refrigeration cycle 10, in which therefrigerant flows from the compressor 12 into the refrigerant passage 24via the heat exchanger 18, heats the temperature-adjusted unit 31,returns to the refrigerant passage 24, and then returns to thecompressor 12 via the expansion valve 16 and the heat exchangers 15, 14.

The vapor compression refrigeration cycle 10 according to the secondembodiment is identical to that of the first embodiment except for thesystem extending from the expansion valve 16 to the heat exchanger 14.More specifically, the refrigerant states from the point A to the pointD via the points B, E, and F on the Mollier chart shown in FIG. 7 areidentical to the refrigerant states from the point A to the point G viathe points B, E, and F on the Mollier chart shown in FIG. 13. Therefore,refrigerant states from the point G to the point A, which are unique tothe vapor compression refrigeration cycle 10 according to the secondembodiment, will be described below.

The refrigerant (point G) reduced in temperature by the expansion valve16 flows into the heat exchanger 15 through the refrigerant passage 27.The wet vapor state refrigerant intermixing saturated liquid andsaturated vapor flows into the tube of the heat exchanger 15. Whileflowing through the tube, the refrigerant absorbs heat from the outsideair via the fin as latent heat of evaporation, and as a result, therefrigerant evaporates while remaining at a constant pressure. Therefrigerant is then heated through heat exchange with the outside air inthe heat exchanger 15, whereby the dryness of the refrigerant increases.When the refrigerant receives the latent heat in the heat exchanger 15,a part thereof vaporizes, leading to an increase in the proportion ofsaturated vapor in the wet vapor state refrigerant (point D).

The wet vapor state refrigerant discharged from the heat exchanger 15flows into the heat exchanger 14 through the refrigerant passage 23. Thewet vapor state refrigerant intermixing saturated liquid and saturatedvapor flows into the tube of the heat exchanger 14. While flowingthrough the tube, the refrigerant absorbs heat from the outside air viathe fin as latent heat of evaporation, and as a result, the refrigerantevaporates while remaining at a constant pressure. When the refrigeranthas turned entirely into dry saturated vapor, the temperature of therefrigerant vapor is raised further by sensible heat, and as a result,the refrigerant vapor turns into superheated vapor (point A).

During a heating operation performed in a cold period, theair-conditioning air is heated, and the temperature-adjusted unit 31 isheated by causing the high-pressure refrigerant to flow into the heatexchange unit 30 and exchange heat with the temperature-adjusted unit31. In a case where the temperature-adjusted unit 31 is an ATF cooler,the ATF can be actively heated such that the temperature of the ATF israised to an appropriate level. As a result, the viscosity of the ATFdoes not increase, and therefore problems such as insufficient gearlubrication and an increase in friction loss can be avoided. Afterpassing through the expansion valve 16, the low-temperature,low-pressure refrigerant is heated at two stages by the two heatexchangers 15, 14, respectively and therefore respective heat exchangecapacities of the heat exchangers 14, 15 can be reduced. The size of theheat exchangers 14, 15 can therefore be reduced accordingly, and as aresult, the heat exchange apparatus 1 obtained herein is small enough tobe suitable for installation in a vehicle.

FIG. 14 is a schematic view showing a configuration of the heat exchangeapparatus 1 according to a third embodiment. The heat exchange apparatus1 according to the third embodiment differs from those of the first andsecond embodiments in that an expansion valve 56 is provided on therefrigerant path between the heat exchanger 14 and the heat exchangeunit 30 as a second pressure reducer differing from the first pressurereducer (the expansion valve 16) in place of the open/close valve 53that sets the refrigerant passages 52, 54 in a communicative ornon-communicative condition. Similarly to the expansion valve 16, theexpansion valve 56 reduces the temperature and pressure of therefrigerant by expanding the high-pressure liquid phase refrigerant thatis discharged from the heat exchanger 14. The heat exchange apparatus 1also includes a refrigerant passage 57 serving as a refrigerant paththat bypasses the expansion valve 56, and an open/close valve 58provided in the refrigerant passage 57 to switch the refrigerant flow tothe refrigerant passage 57.

During the cooling operation, as shown in FIG. 14, the open/close valve58 is closed. Accordingly, the refrigerant condensed in the heatexchanger 14 flows toward the heat exchange unit 30 through therefrigerant passage 52, the expansion valve 56, and the refrigerantpassage 54. The refrigerant that flows into the heat exchange unit 30 soas to pass through the cooling passage 32 cools the temperature-adjustedunit 31 by drawing heat from the temperature-adjusted unit 31. Hence,the heat exchange unit 30 cools the temperature-adjusted unit 31 usingthe low-temperature, low-pressure refrigerant discharged from the heatexchanger 14 and reduced in pressure by the expansion valve 56.

FIG. 15 is a Mollier chart showing states of the refrigerant during thecooling operation of the vapor compression refrigeration cycle 10according to the third embodiment. An abscissa in FIG. 15 shows thespecific enthalpy (unit: kJ/kg) of the refrigerant, while an ordinateshows the absolute pressure (unit: MPa) of the refrigerant. A curve inthe diagram is a saturation vapor line and a saturation liquid line ofthe refrigerant. FIG. 15 shows the thermodynamic state of therefrigerant at each point (i.e. points A, B, H, C, D, G, and E) of thevapor compression refrigeration cycle 10, in which the refrigerant flowsinto the refrigerant passage 52 from the refrigerant passage 23 at theoutlet of the heat exchanger 14, flows through the refrigerant passage54 after being expanded in the expansion valve 56, cools thetemperature-adjusted unit 31, and then returns to the refrigerantpassage 23 at the inlet of the heat exchanger 15 from the refrigerantpassage 55.

The vapor compression refrigeration cycle 10 according to the thirdembodiment is identical to that of the second embodiment except for thesystem extending from the heat exchanger 14 to the expansion valve 16.More specifically, the refrigerant states from the point E to the pointC via the points A and B on the Mollier chart shown in FIG. 9 areidentical to the refrigerant states from the point E to the point H viathe points A and B on the Mollier chart shown in FIG. 15. Therefore,refrigerant states from the point H to the point E, which are unique tothe vapor compression refrigeration cycle 10 according to the thirdembodiment, will be described below.

The refrigerant (point H) liquefied in the heat exchanger 14 flows intothe expansion valve 56 through the refrigerant passages 23, 52. In theexpansion valve 56, the saturated liquid-form refrigerant isthrottle-expanded such that the temperature and pressure of therefrigerant fall while the specific enthalpy thereof remains unchanged.As a result, the refrigerant turns into wet vapor intermixing saturatedliquid and saturated vapor (point C). The refrigerant reduced intemperature in the expansion valve 56 flows into the cooling passage 32of the heat exchange unit 30 via the refrigerant passage 54, and coolsthe temperature-adjusted unit 31. The refrigerant is heated by the heatexchange performed with the temperature-adjusted unit 31, and as aresult, the dryness of the refrigerant increases. The refrigerantreceives latent heat from the temperature-adjusted unit 31 so as toundergo partial vaporization, leading to an increase in the proportionof saturated vapor in the wet vapor state refrigerant (point D).

The refrigerant then flows into the heat exchanger 15. The wet vapor ofthe refrigerant is condensed again in the heat exchanger 15, and whencondensed entirely, the refrigerant forms a saturated liquid. Further,the refrigerant discharges sensible heat so as to form a supercooledliquid (point G). The refrigerant then passes through the expansionvalve 16, in which the supercooled liquid state refrigerant isthrottle-expanded such that the temperature and pressure of therefrigerant fall while the specific enthalpy thereof remains unchanged.As a result, the refrigerant forms low-temperature, low-pressure wetvapor in a gas-liquid mixed state (point E).

In the heat exchange apparatus 1 according to the third embodiment, thetemperature-adjusted unit 31 can be cooled during the cooling operationusing refrigerant that has been expanded by the expansion valve 56 so asto decrease in temperature, and therefore the temperature-adjusted unit31 can be cooled more efficiently. By selecting optimal specificationsfor the expansion valve 56, the temperature of the refrigerant thatcools the temperature-adjusted unit 31 can be adjusted as desired by theheat exchange unit 30. Hence, the temperature-adjusted unit 31 can becooled by supplying refrigerant having a lower temperature, which ismore suitable for cooling the temperature-adjusted unit 31, to the heatexchange unit 30.

FIG. 16 is a schematic view showing the heat exchange apparatusaccording to the third embodiment in a condition where the four-wayvalve has been switched. When a heating operation is performed using theheat exchange apparatus 1 according to the third embodiment, theexpansion valve 56 is fully closed (set at opening 0%) and theopen/close valve 58 is opened. Accordingly, the refrigerant flowsthrough the vapor compression refrigeration cycle 10 so as to passsequentially through a point A, a point B, a point E, a point G, a pointD, and a point C, as shown in FIG. 16. Thus, the refrigerant circulatesbetween the compressor 12, the heat exchanger 18, the expansion valve16, and the heat exchangers 15, 14.

At this time, the refrigerant circulates through the vapor compressionrefrigeration cycle 10 while the state thereof is varied in a similarmanner to that shown in FIG. 11. Hence, similarly to the secondembodiment, the refrigerant is heated by both the heat exchange unit 30and the heat exchangers 14, 15 such that the refrigerant can be heatedto a sufficient superheated vapor state at the outlet of the heatexchanger 14, and therefore the temperature-adjusted unit 31 can becooled appropriately while maintaining a superior heating performancewith respect to the passenger compartment of the vehicle.

FIG. 17 is a schematic view showing the heat exchange apparatus 1 whenthe temperature-adjusted unit 31 according to the third embodiment isheated. When the temperature-adjusted unit 31 is heated during a heatingoperation performed in a cold period using the heat exchange apparatus 1according to the third embodiment, the expansion valve 56 is fullyclosed (set at opening 0%), the open/close valve 58 is closed, and theopen/close valve 63 is opened. Accordingly, the refrigerant flowsthrough the vapor compression refrigeration cycle 10 so as to passsequentially through points A, B, E, F, G, and D, as shown in FIG. 17.Thus, the refrigerant circulates between the compressor 12, the heatexchanger 18, the expansion valve 16, and the heat exchangers 15, 14.

At this time, the refrigerant circulates through the vapor compressionrefrigeration cycle 10 while the state thereof is varied in a similarmanner to that shown in FIG. 13. Hence, similarly to the secondembodiment, during a heating operation performed in a cold period, theair-conditioning air can be heated, and the temperature-adjusted unit 31can be heated by introducing the high-pressure refrigerant into the heatexchange unit 30. In a case where the temperature-adjusted unit 31 is anATF cooler, the ATF can be actively heated, whereby the temperature ofthe ATF can be raised to an appropriate level. As a result, theviscosity of the ATF does not increase, and therefore problems such asinsufficient gear lubrication and an increase in friction loss can beavoided.

Note that in the first to third embodiments, the heat exchange apparatus1 that adjusts the temperature of the temperature-adjusted unitinstalled in the vehicle to an optimum temperature was described usingan ATF cooler as an example. However, the temperature-adjusted unit 31subjected to temperature adjustment by the heat exchange apparatus 1according to the invention is not limited to an ATF cooler installed ina vehicle, and any device that requires cooling or heating in accordancewith various conditions such as outside air temperature, or a heatgenerating part of such a device, may be used instead.

Embodiments of the invention were described above, but theconfigurations of the respective embodiments may be combinedappropriately. Further, the embodiments disclosed herein are exampleswith respect to all points, and are not therefore to be consideredlimiting. The scope of the invention is defined by the scope of theclaims rather than the above description, and is intended to includeequivalent definitions to the scope of the claims and all modificationswithin that scope.

The heat exchange apparatus according to the invention is particularlysuitable for use in adjusting the temperature of a temperature-adjustedunit, such as an ATF cooler that requires cooling or heating, using avapor compression refrigeration cycle that heats and cools a vehicleinterior of a vehicle.

1. A heat exchange apparatus that performs heat exchange between a refrigerant and a temperature-adjusted unit, comprising: a compressor configured to compress the refrigerant in order to circulate the refrigerant through the heat exchange apparatus; a first heat exchanger configured to perform heat exchange between the refrigerant and outside air; a first pressure reducer configured to reduce a pressure of the refrigerant; a second heat exchanger configured to perform heat exchange between the refrigerant and air-conditioning air; and a first flow control valve configured to adjust a flow rate of the refrigerant, wherein a first passage provides a path for the refrigerant to flow between the first heat exchanger and the first pressure reducer, a second passage provides a path for the refrigerant to flow between the first pressure reducer and the second heat exchanger, a third passage is connected in parallel with the first passage on the refrigerant path between the first heat exchanger and the first pressure reducer, the first flow control valve adjusts the flow rate of the refrigerant flowing through the first passage and the flow rate of the refrigerant flowing through the third passage, and the temperature-adjusted unit is disposed to exchange heat with the refrigerant flowing through the first passage and to exchange heat with the refrigerant flowing through the second passage.
 2. The heat exchange apparatus according to claim 1, further comprising: a four-way valve configured to switch between a refrigerant flow from the compressor to the first heat exchanger and a refrigerant flow from the compressor to the second heat exchanger.
 3. (canceled)
 4. The heat exchange apparatus according to claim 1, further comprising: a second flow control valve configured to adjust a flow rate of the refrigerant, wherein a fourth passage is connected in parallel with the second passage on the refrigerant path between the first pressure reducer and the second heat exchanger; and the second flow control valve adjusts the flow rate of the refrigerant flowing through the second passage and the flow rate of the refrigerant flowing through the fourth passage.
 5. The heat exchange apparatus according to claim 1, further comprising: a first open/close valve configured to open and close the first passage.
 6. The heat exchange apparatus according to claim 4, further comprising: a second open/close valve configured to open and close the second passage.
 7. The heat exchange apparatus according to claim 6, wherein the second open/close valve is closed when the first open/close valve is open and the second open/close valve is open when the first open/close valve is closed.
 8. The heat exchange apparatus according to claim 1, further comprising: a second pressure reducer configured to reduce the pressure of the refrigerant, the second pressure reducer being provided in the first passage between the first heat exchanger and the temperature-adjusted unit.
 9. The heat exchange apparatus according to claim 8, further comprising: a third open/close valve configured to open and close a passage for the refrigerant, wherein a fifth passage is connected in parallel with a path passing through the second pressure reducer on a path that forms a part of the first passage and passes through the temperature-adjusted unit and the first heat exchanger, and the third open/close valve that is provided in the fifth passage in order to open and close the fifth passage. 